Covalent bonds typically form between the atoms of elements that share A. nuclei
B. oppositely charged ions
C. protons
D. valence electrons

The carbon dioxide enters the leaves of the plant through small pores called stomata.

Explanation:

The plant uses sunlight as energy to perform this chemical reaction. Photosynthesis separates carbon dioxide and water — known as CO2 and H2O, respectively — into their individual molecules and combines them into new products.